Exposure apparatus for transferring a mask pattern onto a substrate

ABSTRACT

An exposure method for irradiating a mask from above the mask held in proximity to a substrate positioned below the mask to transfer a mask pattern of the mask to a photosensitive layer of the substrate by exposing the photosensitive layer to a light beam, includes the steps of using a gap-measuring device to measure a gap between a portion of the mask to be locally scanned and irradiated and a portion of the substrate to be locally irradiated, comparing a value measured by the gap-measuring device with a preset value, and locally deforming the mask and/or the substrate according to a difference between the value measured by the gap-measuring device and the preset value so as to cause the gap to approach a predetermined value.

This is a Divisional of parent application Ser. No. 08/404,768, filedMar. 15, 1995 now U.S. Pat. No. 5,573,877.

BACKGROUND OF THE INVENTION

The present invention relates to an exposure method to be used inmanufacturing semiconductor devices or liquid crystal displays and anexposure apparatus for carrying out the method.

Proximity exposure methods are used to transfer a mask pattern of a maskto photosensitive agent applied to a surface of a glass substrate(hereinafter referred to as substrate) or a wafer held in proximity tothe mask by irradiating the mask by a light beam emitted by a lightsource positioned above the mask. Comparing the proximity exposuremethods with projection exposure methods, the former can be carried outat a lower cost than the latter because the former do not require acomplicated lens system or a stage which can be operated with highaccuracy. Further, unlike contact exposure methods, the mask does notcontact the substrate in the proximity exposure methods. Thus, thephotosensitive agent can be prevented from being damaged or torn offfrom the substrate, and hence, failure does not occur. In the proximityexposure methods, the resolution of an image formed by transfer dependsgreatly on the gap between the mask and the substrate.

Supposing that the wavelength of a light beam emitted by a light sourceis λ and the gap between the mask and the substrate is (g), a minimumline width (ds) of the image formed by transfer is expressed as follows:##EQU1##

In order to resolve a line having a width of approximately 3 μm by usinga mercury lamp as a light source, it is necessary to adjust the gapbetween the mask and the substrate to as close as approximately 10 μm.Generally, the substrate is wavy in an extent of approximately 10 μmthrough 20 μm. Thus, it is necessary to adjust the gap between the maskand the substrate very precisely in consideration of this waviness. Tothis end, a complicated construction is required. A method of using asubstrate-flattening chuck for keeping the upper surface of thesubstrate flat by deforming it is known as disclosed in JapaneseLaid-Open Patent Publication No. 59-17247.

An example of a conventional proximity exposure method and aconventional apparatus for carrying out the proximity exposure methodare described below with reference to FIG. 20.

In the conventional proximity exposure apparatus essentially, there areprovided an exposure station 115 and a height-measuring station 116. Indetail, the apparatus comprises a guide rail 112 constituting the baseof the apparatus; a mask height-measuring device 114 installed on theguide rail 112 and movable in an X-direction along the guide rail 112 insliding contact therewith; an X-stage 11 installed on the guide rail 112and movable in the X-direction along the guide rail 112 in slidingcontact therewith; a Z-stage 110 connected with the X-stage 111; aflattening chuck 109 installed on the Z-stage 110; a plurality ofvertically movable elements 118 provided inside the flattening chuck109; a substrate 20 sucked to and held by the flattening chuck 109; amask 21 held in proximity to the substrate 20; a mask chuck 18 forsucking the mask 20 thereto and holding it thereon; an alignment scope19 fixed to an upper portion positioned above the mask 21; a substrateheight-measuring device 113 installed at a position opposed to thesubstrate 20; a mercury lamp 11; a reflection mirror 12; a fly eye lens103; a condensing lens 104; a substrate stage 117 composed of theflattening chuck 109, the Z-stage 110, and the X-stage 111.

The operation of the conventional proximity exposure apparatus havingthe above-described construction is described below.

The substrate stage 117 on which the substrate 20 has been placed ismoved to the height-measuring station 116 along the guide rail 112.Then, the substrate height-measuring device 113 installed above thesubstrate 20 measures the height of the upper face of the substrate 20.The mask height-measuring device 114 moves to the exposure station 115along the guide rail 112, thus measuring the height of the lower face ofa mask 21. Based on the measured values, the level of the verticallymovable elements 118 provided inside the flattening chuck 109 and thatof the Z-stage 110 are adjusted so as to set a gap between the mask 21and the substrate 20 at respective measured positions to a desiredvalue. Then, the substrate stage 117 is moved to the exposure station115, and the substrate 20 and the mask 21 are placed in position byusing the alignment scope 19'. A light beam emitted by the mercury lamp11 is reflected by the reflection mirror 12 to guide it to the fly eyelens 103 to make the diameter thereof uniform. Then, the light beam isadjusted to be parallel to expose the photosensitive layer formed on thesubstrate 20 to a light beam through the mask 21 supported by the maskholder 18.

The above-described conventional proximity exposure apparatus having theconstruction is an exposure type apparatus in which a substrate isexposed to a light beam through a mask by one exposure operation. Thus,it is difficult to compensate the magnification of the mask pattern. Inaddition, it is necessary to provide the apparatus with theheight-measuring station 116 separately from the exposure station 115.Thus, the apparatus is large. Moreover, if the large substrate 20 isused, it is necessary to use the condensing lens having a largediameter. Hence, the apparatus is manufactured at a high cost. Further,the mechanical accuracy of the guide rail is important for accuratelymeasuring the gap between the substrate 20 and the mask 21.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide animproved exposure method capable of compensating the magnification of amask pattern of a mask and forming an image of the mask pattern having ahigh resolution on a photosensitive layer of a substrate by exposing thephotosensitive layer to a light beam and to provide a compact andinexpensive exposure apparatus for carrying out the exposure method.

In accomplishing the above and other objects, according to a firstaspect of the present invention, there is provided an exposure methodfor irradiating a mask from above the mask held in proximity to asubstrate to transfer a mask pattern of the mask to a photosensitivelayer of the substrate by exposing the photosensitive layer to a lightbeam, comprising the steps of:

measuring, by a gap-measuring device, a gap between a portion of themask locally scanned and irradiated and a portion of the substratelocally irradiated;

comparing a value measured by the gap-measuring device with a presetvalue; and

deforming the mask and/or the substrate locally according to adifference between the value measured by the gap-measuring device andthe preset value so as to cause the gap to approach a predeterminedvalue.

According to a second aspect of the present invention, there is providedan exposure apparatus for irradiating a mask from above the mask held inproximity to a substrate to transfer a mask pattern of the mask to thesubstrate by exposing the substrate to a light beam, comprising:

a locally-irradiating means, for scanning the mask from above the mask,having a mask-deforming means for flexing the mask locally by a staticpressure so as to cause the mask and the substrate to relativelyapproach each other;

a gap-measuring means for measuring a gap between the mask and thesubstrate at a portion of the mask irradiated by the locally-irradiatingmeans and at a portion of the substrate irradiated thereby; and

a control means for controlling the mask-deforming means, based on avalue measured by the gap-measuring means and a preset value.

According to a third aspect of the present invention, there is providedan exposure apparatus for irradiating a mask from above the mask held inproximity to a substrate to transfer a mask pattern of the mask to thesubstrate by exposing the substrate to a light beam, comprising:

a locally-irradiating means for scanning the mask from above the mask;

a gap-measuring means for measuring a gap between the mask and thesubstrate at a portion of the mask irradiated by the locally-irradiatingmeans and at a portion of the substrate irradiated thereby;

a chuck comprising a slight-moving means for sucking and holding thesubstrate and vertically moving a portion of the mask to be irradiatedby the locally-irridating means so as to cause the substrate and themask to approach each other locally; and

a control means for controlling the slight-moving means based on a valuemeasured by the gap-measuring means and a preset value.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings, in which:

FIG. 1 is a sectional view showing an exposure apparatus according to afirst embodiment of the present invention;

FIG. 2 is a view showing the sectional configuration of a light beamprojected by a locally-irradiating means and a scanning path accordingto the first embodiment of the present invention;

FIG. 3 is a perspective view of one specific example of the uniformexposure system of the locally-irradiating means so as to perform theexposure shown in FIG. 14;

FIG. 4 shows examples of the illumination distribution of the exposurelight beam indicating the relationship between the illumination and theposition in the Y direction on the scanning area; the transmittancedistribution of the ND filter indicating the relationship between thetransmittance and the position in the Y direction; and the exposure areaof the light beam;

FIGS. 5 and 6 is a partially sectional side view and an explodedperspective view of one specific example of the chuck;

FIG. 7 is a bottom view of a nozzle of the locally-irradiating means;

FIG. 8 is an explanatory view showing the static pressure applied to thesubstrate by the nozzle;

FIG. 9 is a plan view of the substrate with twelve cross-shapedalignment marks;

FIG. 10 is a plan view of the mask twelve cross-shaped alignment marks;

FIG. 11 is a plan view showing a condition where the substrate and themask overlap each other;

FIG. 12 is a partly enlarged sectional view showing an exposureapparatus according to a second embodiment of the present invention;

FIG. 13 is a sectional view showing an exposure apparatus according to athird embodiment of the present invention;

FIG. 14 is a view showing the sectional configuration of a light beamprojected by a locally-irradiating means and an illuminancedistribution;

FIG. 15 is a partly enlarged sectional view showing a modification inwhich the position of a gap-measuring means according to the firstembodiment is altered;

FIG. 16 is a partly enlarged sectional view showing a modification inwhich the alignment scope according to the first embodiment is providedat the locally-irradiating means;

FIG. 17 is a sectional view showing an exposure apparatus according to afourth embodiment of the present invention;

FIG. 18A is a partially enlarged view of the exposure apparatus forexplaining a calibration function;

FIG. 18B is an enlarged view of a part of FIG. 18A;

FIG. 19 is a perspective view showing a mask; and

FIG. 20 is a schematic view showing a conventional proximity exposureapparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

An exposure method and an exposure apparatus according to a firstembodiment of the present invention are described below with referenceto FIGS. 1 and 2. FIG. 1 is a sectional view showing an exposureapparatus according to the first embodiment of the present invention.FIG. 2 is a view showing the sectional configuration of a light beamprojected by a locally-irradiating means and a scanning path accordingto the first embodiment of the present invention.

Referring to FIG. 1, the exposure apparatus is constructed as follows. AY-axis guide 2 is fixed to a frame 1. A Y-stage 38 is installed on theY-axis guide 2 and is movable in a Y-direction in sliding contacttherewith. An X-axis guide 3 is fixed to the Y-stage 38. An X-stage 4 isinstalled on the X-axis guide 3 and is movable in an X-direction insliding contact therewith. An irradiation Z-stage 5 is installed on theX-stage 4 and is movable in a Z-direction in sliding contact therewith.A servo motor 30 is fixed to the X-stage 4. One end of a ball thread 29is connected with the irradiation Z-stage 5 and the other end thereof isconnected with the servo motor 30. A locally-irradiating means 6 isfixed to the irradiation Z-stage 5. One end of an air pressure pipe 7 isconnected with the locally-irradiating means 6 and the other end thereofis connected with an air pressure source 36. One end of an optical fiber8 is connected with the locally-irradiating means 6. A reflection mirror12 condenses light beams emitted by a mercury lamp 11. A lens 22 isfixed to the inside of the locally-irradiating means 6. Asensor-provided X-stage 10 is installed on the X-axis guide 3 and ismovable in the X-direction in sliding contact therewith. A gap-measuringmeans 9 is fixed to the sensor-provided stage 10. An XYθ stage 13 isinstalled on the frame 1 and is movable in an XY-plane in slidingcontact therewith. A Z-stage 14 is installed on the XYθ stage 13 and ismovable in the Z-direction. A chuck 15 is fixed to the Z-stage 14. Asubstrate 20 is sucked to and held by the chuck 15. One end of a maskframe 16 is fixed to the frame 1 and the other end thereof is connectedwith a mask chuck 18. A mask 21 is sucked to and held by the mask chuck18. One end of each of two brackets 17 is connected with the mask frame16 and the other end thereof is installed on an alignment scope 19 suchthat the other end is movable in the X-direction in sliding contacttherewith. A control means 37 comprises a gap-setting device 31, acontroller 32, and a servo motor driver 33. One end of the control means37 is connected with the gap-measuring means 9 and the other end thereofis electrically connected with the servo motor 30.

Referring to FIG. 2, reference numeral 52 denotes a scanning path inlocally irradiating the mask 21. Reference numeral 61 denotes a boundaryof light beams. Reference numerals 53, 55, 57, and 59 denote startpoints of first through forth exposure lines. Reference numerals 54, 56,58, and 60 denote termination points of the first through forth exposurelines.

The operation of the exposure apparatus having the above-describedconstruction is described below. Scanning and exposure to be carried outby local irradiation are described below.

Light beams emitted by the mercury lamp 11 are condensed by thereflection mirror 12 and then guided to one end of the optical fiber 8.Light fluxes which have left the other end of the optical fiber 8 areadjusted to be parallel with each other by the lens 22 in thelocally-irradiating means 6 to irradiate the mask 21. Thelocally-irradiating means 6 irradiates the entire surface of the mask 21held over the substrate 20 proximate to the mask 21 and placed at anappropriate position relative to the substrate 20 by using the alignmentscopes 19, while the locally-irradiating means 6 is being moved in theXY-plane above the mask 21 by the X-stage 4, the Y-stage 38, and unshowndriving means thereof. The sectional configuration 62 of a light beamprojected by the locally-irradiating means 6 is trapezoidal which issymmetrical with respect to a center line (symmetry axis) connecting thecenter of the upper side (a) and the lower side (b) of a trapezoid asshown in FIG. 2. The mask 21 is scanned in the direction (X-direction)of the symmetry axis of the trapezoid to expose the mask 21 to a lightbeam along the first exposure line. Then, the mask 21 is exposed to alight beam along the second exposure line in the direction opposite tothe scanning direction along the first exposure line by scanning it inthe direction of the symmetry axis, of an adjacent trapezoid, moved by astep of (a+b)/2 from the first exposure line in a direction(Y-direction) perpendicular to the symmetry axis. Supposing that themovement amount of the symmetry axis is dislocated by ΔY from a targetposition in the Y-direction, the nonuniform irradiation of the boundary61 of the light beams is expressed by 2ΔY/(b-a). The nonuniformirradiation which occurs due to an error in the movement of the Y-stage38 can be decreased by reducing the gradient of the inclined sides ofthe trapezoid and thus the entire surface of the mask 21 can beirradiated uniformly without an unexposed portion being formed thereon.A photosensitive layer of the substrate 20 is exposed to a light beam bymoving the XYθ stage 13 slightly in the same direction as the scanningdirection synchronously with each scanning performed by thelocally-irradiating means 6 so as to accomplish an error distributionand further, adjustably magnify the mask pattern in transferring it tothe photosensitive layer.

As one example of the substrate 20, the size thereof is 380 mm×480 mmand the thickness is 1.1 mm. As one example of the mask 21, the sizethereof is 508 mm×10 mm and the thickness is 3.0 mm.

The method of allowing the gap between the mask 21 and the substrate 20to be locally close to each other is described below. When thelocally-irradiating means 6 is moved to a position over the mask 21 heldin proximity to the substrate 20 by tens of microns by adjusting thelevel of the Z-stage 14, compressed air supplied by the air pressuresource 36 is jetted from a nozzle provided on the outlet of thelocally-irradiating means 6 via the air pressure pipe 7. Consequently,the mask 21 is locally deformed. Supposing that the air is jetted fromthe nozzle at a pressure (P) and that the sectional area of the nozzleis (S), a force is applied to the mask 21 at (PS). Supposing that thesize of the mask 21 is 360 mm×465 mm and the thickness thereof is 4 mm,and that the sectional area of the nozzle is 4 cm², hundreds of gramsare required per cm² to flex the mask 21 by tens of micrometers. Thepressure (P) at the nozzle outlet depends on the distance between thenozzle tip and the mask 21. Thus, the pressure (P) is increased bymoving the irradiation Z-stage 5 downward and hence, the deformationamount of the mask 21 increases.

FIGS. 5 and 6 show one specific example of the chuck 15. The chuck 15includes a base plate 15c, a shim 15b of square frame shape on the baseplate 15c, and a substrate chuck 15a having many holes 15e on the shim15b. The substrate chuck 15a is fixedly connected to the base plate 15cwith many bolts 15d while holding the shim 15b between them. Thus, whenthe substrate 20 is placed on the substrate chuck 15a, the centerportion of the substrate 20 is lowered, for example, by 150 μm ascompared with other portion because of a space surrounded between thesubstrate chuck 15a and the base plate 15c by the shim 15b as shown inFIG. 5.

The nozzle has six through-holes 6b around a hexagonal opening 6a asshown in FIG. 7. The light beam is projected through the opening 6a. Theair is jetted through the through-holes 6b via the air pressure source36 and the air pressure pipe 7 to deform the portion of the mask 21confronting the nozzle by static pressure as shown in FIGS. 5 and 8. Asone example, when the nozzle is used at the center portion of the mask21, the deforming amount of the mask 21 is 150 μm maximum at suppliedpressure of 5 kgf/cm² and 10 μm-interval between the mask and the nozzleof FIG. 7. One example of the nozzle has a 102 mm-outer diameter, 56.3mm-distance between confronting inner walls of the opening and thethrough-hole of a 0.3 mm-inner diameter.

The positioning method of the mask 21 and the substrate 20 is shown inFIGS. 9 through 11. The substrate 20 has twelve cross-shaped alignmentmarks 20a as shown in FIG. 9 and the marks 21 has twelve cross-shapedalignment marks 21a as shown in FIG. 10 in each of which eachcross-shaped alignment marks 20a of the substrate 20 can be inserted.Then, when the mask 21 is positioned to the substrate 20, the mask 21 isadjusted to the substrate 20 so that the twelve cross-shaped alignmentmarks 20a of the substrate 20 can be inserted in the twelve cross-shapedalignment marks 21a of the mask 21 while viewing through the mask 21 asshown in FIG. 11.

The gap-measuring means 9 of laser reflection type measures the gapbetween the mask 21 and the substrate 20, thus outputting a signalindicating the length of the gap to the controller 32. The controller 32compares the value of the signal and the value of a signal outputtedthereto from the setting device 31 with each other. The controller 32outputs a deviation signal to the servo driver 33. The servo driver 33outputs a control signal to the servo motor 30 according to the value ofthe deviation signal. As a result, the irradiation Z-stage 5 is drivenvia the ball thread 29 so as to adjust the deformation amount of themask 21. In this manner, the gap between the mask 21 and the substrate20 can be allowed to be close to a predetermined length locally set. Animage having a high resolution can be formed on the photosensitive layerof the substrate 20 by exposing it to a light beam.

As described above, according to the first embodiment, the exposureapparatus comprises the scan type locally-irradiating means 6 projectingthe light beam trapezoidal in its sectional configuration 62 and havingmask-deforming means comprising the air pressure source 36 and the airpressure pipe 7 for deforming the mask 21 by static pressure; thegap-measuring means 9 for measuring the gap between a portion of themask 21 irradiated by the locally-irradiating means 6 and a portion ofthe substrate 20 irradiated thereby; the control means 37 forcontrolling the mask-deforming means 36 and 7 based on a value measuredby the gap-measuring means 9 and a preset value; and the slight-movingmechanism comprising the XYθ stage 13 for moving the mask 21 and thesubstrate 20 relative to each other synchronously with the scanning ofthe locally-irradiating means 6. This construction allows the mask 21 tobe scanned, with portions of to-be-irradiated regions thereof overlappedwith each other at the boundary of adjacent scanning paths, thusfacilitating the compensation even though the magnification of the maskpattern is inappropriate relative to the substrate, the inappropriatemagnification can be compensated. Accordingly, the photosensitive layercan be exposed to a light beam uniformly and at a high resolution.

An exposure method and an exposure apparatus according to a secondembodiment of the present invention are described below with referenceto FIG. 12 showing the exposure apparatus by partly enlarging it. Thesecond embodiment is different from the first embodiment in that portsare formed in the periphery of the locally-irradiating means 6, and theports are connected with a vacuum source 35 via a vacuum pipe 25 so asto constitute suction ports. The suction ports are capable of liftingthe periphery of a to-be-irradiated portion of the mask 21 by a negativepressure so as to deform the mask 21 more locally than the firstembodiment. In this manner, the mask 21 and the substrate 20 can bepositioned in proximity to each other to an extent greater than thefirst embodiment. As described above, The provision of the suction portsallows the photosensitive layer to be exposed to a light beam at ahigher resolution. The other constructions of the apparatus according tothe second embodiment are the same as those of the apparatus accordingto the first embodiment.

An exposure method and an exposure apparatus according to a thirdembodiment of the present invention are described below with referenceto FIGS. 13 and 14. FIG. 13 is a sectional view showing an exposureapparatus according the third embodiment. FIG. 14 is a view showing thesectional configuration of a light beam projected locally by thelocally-irradiating means 6 to the mask 21 and an illuminancedistribution. The third embodiment is different from the firstembodiment in that not the mask 21 but the substrate 20 is deformed tocause the substrate 20 and the mask 21 to approach each other locally.An elastic chuck 26 made of an aluminum plate or a stainless steel plateis used instead of the chuck 15 of the first embodiment; a piezo-driver34 is used instead of the servo motor driver 33 of the first embodiment;a piezo-X-stage 40 is provided instead of the X-stage 4 of the firstembodiment; one end of a piezo-actuator 28 is connected with a roller27; the other end of the piezo-actuator 28 is connected with thepiezo-X-stage 40; and the gap-measuring means 9 and thelocally-irradiating means 6 are fixed to the X-stage 4. The sectionalconfiguration 77 of each light beam projected by the locally-irradiatingmeans 6 is rectangular as shown in FIG. 14. The illuminance distributionof the light beam is trapezoidal as shown by reference numerals 71through 74 of FIG. 14. This construction allows an output signal of thegap-measuring means 9 to be fed back to the piezo-actuator 28 via thecontrol means 37, thus causing the substrate 20 and the mask 21 toapproach each other locally, with a predetermined gap providedtherebetween. This construction allows the photosensitive layer to beexposed to a light beam at a high resolution. The illuminancedistribution of the light beam is trapezoidal as shown by referencenumerals 71 through 74 of FIG. 14, which provides an advantage similarto that provided by the trapezoidal configuration of the light beam,thus allowing the photosensitive layer to be uniformly exposed.

FIG. 3 shows a perspective view of one specific example of the uniformexposure system of the locally-irradiating means 6 so as to perform theexposure shown in FIG. 14. In FIG. 3, the uniform light beam 200 fromthe lens 22 passes through an ND filter (neutral density filter) 201 toirradiate onto the substrate 20. Reference numeral 202 denotes anexposure area of the light beam and 203 denotes a scanning path of thelight beam. FIG. 4 shows examples of the illumination distribution ofthe exposure light beam indicating the relationship between theillumination and the position in the Y direction on the scanning area;the transmittance distribution of the ND filter) 201 indicating therelationship between the transmittance and the position in the Ydirection; and the exposure area 202 of the light beam. That is, the NDfilter 201 having the above trapezoidal transmittance distribution isarranged between the lens 22 and the substrate 20 to form the light beamhaving the rectangular sectional configuration 77 and having thetrapezoidal irradiation energy shown in FIG. 14.

As described above, according to the third embodiment, the sectionalconfiguration 62 of a light beam is trapezoidal. The exposure apparatuscomprises the scan type locally-irradiating means 6 projecting the lightbeam having the trapezoidal configuration in the illuminancedistribution; the gap-measuring means 9 for measuring the gap between aportion of the mask 21 irradiated by the locally-irradiating means 6 anda portion of the substrate 20 irradiated thereby; the chuck 26comprising the piezo-actuator 28 serving as the slight-moving means forsucking the substrate 20 and holding it thereon and moving ato-be-irradiated portion of the mask 21 vertically so as to approach thesubstrate 20 and the mask 21 to each other locally; the control means 37for controlling the slight-moving means 28 based on a value measured bythe gap-measuring means 9 and a preset value; and the slight-movingmechanism comprising the XYθ stage 13 for moving the mask 21 and thesubstrate 20 to each other synchronously with the scanning of thelocally-irradiating means 6. This construction allows the mask 21 to bescanned, with portions of to-be-irradiated regions thereof overlappedwith each other at the boundary of adjacent scanning paths, thusfacilitating the compensation of the magnification of the pattern mask.Accordingly, the photosensitive layer can be exposed to a light beamuniformly and at a high resolution.

The sectional configuration 62 of the light beam is trapezoidal in thefirst embodiment, but needless to say, it may be parallelorgammatic orhexagonal. The gap-measuring means 9 is installed on the sensor-providedX-stage in the first embodiment, but it may be installed on the X-stage4 as shown in FIG. 15. Although the XYθ stage 13 is used to cause thesubstrate 20 and the mask 21 to approach each other, with apredetermined gap provided therebetween in the first embodiment, themoving means may be provided on the mask side. Although the irradiationZ-stage 5 to be driven by the servo motor 30 via the ball thread 29 isprovided as the means for adjusting the static pressure (P) in the firstand second embodiments, a pressure adjusting means for controlling thepressure of compressed air to be supplied from the air pressure source36 may be provided. Needless to say, the pressure adjusting meansprovides an advantage similar to that provided by the irradiationZ-stage 5.

Although the alignment scopes 19 are fixed to the upper portionpositioned above the mask 21 in the embodiments, one alignment scope 19can be provided at the locally-irradiating means 6 as shown in FIG. 16.FIG. 16 shows the control system of the XYθ stage 13 as a result of thedetection of the alignment scope(s) 19 which can be applied to the aboveembodiments. According to the control system, the alignment scope 19 isconnected to an image processing device 138 for processing images of thealignment marks 20a and 21a of the substrate 20 and mask 21 picked-upthrough the alignment scope 19. The result of the processing isoutputted from the image processing device 138 to a controller 139 forcontrolling motor drivers 217 of the XYθ stage 13.

According to the embodiments, the mask and the substrate are locallyirradiated. Thus, it is unnecessary to use a condensing lens having alarge diameter. The mask and/or the substrate are locally deformed ateach scanning position thereof, with the mask and the substrate held inproximity to each other locally, based on a value measured by thegap-measuring means so as to allow the gap between the mask and thesubstrate to be coincident with a preset value. Therefore, the gap canbe reliably allowed to be coincident with the preset value in the entireregion to be exposed to a laser beam, and hence, an image having a highresolution can be formed on the substrate by exposing the photosensitivelayer of the substrate to a light beam.

According to the embodiments, the exposure apparatuses being compact andhaving a simple construction and capable of resolving the pattern maskat a high resolution can be provided.

According to the embodiment, the photosensitive layer is exposed to alight beam by moving the mask and the substrate relative to each otherto a slight extent, synchronously with each scanning performed by thelocally-irradiating means. Therefore, it is possible to distribute anerror which may occur due to an inappropriate magnification of the maskpattern relative to the substrate so as to compensate the inappropriatemagnification of the mask pattern.

According to the embodiment, although the locally-irradiating means ofscan type is used, the mask is scanned, with portions ofto-be-irradiated regions thereof overlapped with each other at theboundary of adjacent scanning paths so as to distribute irradiationenergy uniformly to the entire region of the mask to be irradiated.Accordingly, the entire photosensitive layer can be exposed to a lightbeam uniformly.

An exposure method and an exposure apparatus according to a fourthembodiment of the present invention are described below with referenceto FIGS. 17 through 19. FIG. 17 is a sectional view showing an exposureapparatus according to the fourth embodiment of the present invention.FIG. 18A is a partially enlarged view showing the exposure apparatus forexplaining a calibration function. FIG. 18B is a partially more enlargedview of a part of the exposure apparatus for explaining the calibrationfunction. FIG. 19 is a perspective view showing a mask as viewed fromabove the mask pattern.

Referring to FIG. 17, the proximity exposure apparatus is constructed asfollows. A Y-axis guide 2 is fixed to a frame 1. A Y-stage 4 isinstalled on the Y-axis guide 2 and is movable in a Y-direction insliding contact therewith. An X-axis guide 3 is fixed to the Y-stage 4.An X-stage 5 is installed on the X-axis guide 3 and is movable in anX-direction in sliding contact therewith. A locally-illuminating means 6is fixed to the X-stage 5. A mask face-measuring means 90, of laserreflection type, comprises a light-projecting laser element 9a and alight-receiving element 9b both fixed to the X-stage 5. One end of anoptical fiber 8 is connected with the locally-illuminating means 6. Areflection mirror 12 condenses light beams emitted by a mercury lamp 11.A lens 7 is fixed to the inside of the locally-illuminating means 6. Asensor-provided X-stage 25 is installed on the X-axis guide 3 and ismovable synchronously with the movement of the X-stage 5 in theX-direction in sliding contact with the X-axis guide 3. A substrateface-measuring means 210, of laser reflection type, comprises alight-projecting laser element 210a and a light-receiving element 210bboth fixed to the X-stage 25. An XYθ stage 13 is installed on the frame1 and is movable in an XY-plane in sliding contact therewith. Three ormore piezo-actuators 215 are connected with the XYθ stage 13. A Z-stage14 is installed on the piezo-actuators 215 and is movable in aZ-direction. A gap-adjusting means 31 comprises the piezo-actuators 215and the Z-stage 14. A quartz chuck 26 is fixed to the Z-stage 14. Asubstrate 20 is sucked to and held by the quartz chuck 26. A thin film22 consists of such as a chrome thin film not transmitting lighttherethrough and is formed on the substrate 20. One end of a mask frame16 is fixed to the frame 1 and the other end thereof is connected withthe mask chuck 18. A mask 21 is sucked to and held by the mask chuck 18.A mask pattern 23a of chromium etc. is formed on a base material 23b ofglass etc. of the mask 21. A light-transmitting gap-measuring window 24is formed at a portion of the mask pattern 23a. One end of each of twobrackets 17 is connected with the mask frame 16 and the other endthereof is installed on an alignment scope 19 and is movable in theX-direction in sliding contact therewith. A control means 37 comprises agap-setting device 32, a controller 33, and a piezo-driver 34. One endof the control means 37 is electrically connected with the maskface-measuring means 90 and the substrate face-measuring means 210 andthe other end thereof is electrically connected with the piezo-actuators215. In this embodiment, the mask face-measuring means 90 and thesubstrate face-measuring means 210 constitute the gap-measuring means incooperation with each other.

The exposure method to be carried out by using the exposure apparatushaving the above-described construction is described below.

Light beams emitted by the mercury lamp 11 are condensed by thereflection mirror 12 and then guided to one end of the optical fiber 8.Light fluxes which have left the other end of the optical fiber 8 areadjusted to be parallel with each other by the lens 7 in thelocally-illuminating means 6 to irradiate the mask 21. Thelocally-illuminating means 6 irradiates the surface of the mask 21 heldover the substrate 20 proximate to the mask 21 and placed at anappropriate position relative to the substrate 20 by using the alignmentscopes 19, while the locally-illuminating means 6 is being moved in theXY-plane above the mask 21 by the X-stage 5, the Y-stage 4, and unshowndriving means thereof.

The method of adjusting the gap between the substrate 20 and the mask 21is described below with reference to FIGS. 17 and 18. First, the X-stage5 and the Y-stage 4 are moved above the gap-measuring window 24 so thatthe mask face-measuring means 90 measures the upper face (P) (measuredvalue B) of the thin film 22 formed on the substrate 20, and thesubstrate face-measuring means 210 measures the lower face Q (measuredvalue C) of the thin film 22. The difference (B-C) is stored by thecontroller 33 as an offset value (F). That is, the offset value (F) ismeasured by the gap-measuring means comprising the mask face-measuringmeans 90 and the substrate face-measuring means 210 and then stored bythe controller 33. Then, the X-stage 5 is moved to a portion other thanthe portion positioned above the gap-measuring window (calibrationwindow) 24, so that the mask face-measuring means 90 measures the lowerface (R) (measured value A) of the mask 21. Then, the measured values(A) and (C) are inputted to the controller 33 so as to find the lengthof the gap between the mask 21 and the substrate 20 by performingcalculation of A-C-F. The length of the gap thus found and a value (D)preset in the gap-setting device 32 are compared with each other. Uponreceipt of a signal indicating the deviation, the piezo-drive 34transmits a control signal corresponding to the deviation signal to thepiezo-actuators 215 so as to drive the Z-stage 14, thus allowing thesubstrate 20 and the mask 21 to be moved at positions proximate to eachother with a predetermined interval provided therebetween. In thismanner, the gap between the mask 21 and the substrate 20 is adjusted ateach to-be-scanned position of the mask 21. Thus, the photosensitivelayer of the substrate 20 can be exposed to a laser beam at a highresolution.

The gap between the substrate 20 and the mask 21 is measured byutilizing the gap-measuring window 24 provided on the mask side. But itis possible to measure the gap by utilizing the gap-measuring windowprovided on the substrate side. Further, the gap-measuring means may beprovided independently of the mask face-measuring means 90 and thesubstrate face-measuring means 210.

According to the proximity exposure method and proximity exposureapparatus for carrying out the method, a value measured by the maskface-measuring means and a value measured by the substrateface-measuring means are calibrated in advance by using a value measuredby the gap-measuring means. Thus, the gap between the substrate and themask can be indirectly measured by the mask face-measuring means and thesubstrate face-measuring means even though a thin film not transmittinga laser beam therethrough is formed on a substrate and/or a mask.Therefore, the gap between the substrate and the mask can be adjustedaccurately at each scanned position. Thus, an image having a highresolution can be formed on the entire exposed region by transfer.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. An exposure apparatus for irradiating a mask fromabove the mask held in proximity to a substrate to transfer a maskpattern of the mask to the substrate by exposing the substrate to alight beam, comprising:a locally-irradiating means, for scanning themask from above the mask, having a mask-deforming means for flexing themask locally by a static pressure so as to cause the mask and thesubstrate to each other; a gap-measuring means for measuring a gapbetween the mask and the substrate at a portion of the mask irradiatedby the locally-irradiating means and at a portion of the substrateirradiated thereby; and a control means for controlling themask-deforming means, based on a value measured by the gap-measuringmeans and a preset value.
 2. The exposure apparatus as claimed in claim1, wherein an air jetting means for jetting air to the mask to move themask upward by a negative pressure is provided in a periphery of themask-deforming means.
 3. The exposure apparatus as claimed in claim 1,wherein a suction means for drawing the mask upward by a negativepressure is provided in a periphery of the mask-deforming means.
 4. Anexposure apparatus for irradiating a mask from above the mask held inproximity to a substrate to transfer a mask pattern of the mask to thesubstrate by exposing the substrate to a light beam, comprising:alocally-irradiating means for scanning the mask from above the mask; agap-measuring means for measuring a gap between the mask and thesubstrate at a portion of the mask irradiated by the locally-irradiatingmeans and at a portion of the substrate irradiated thereby; a chuckcomprising a slight-moving means for drawing and holding the substrateand vertically moving a portion, of the mask, to be irradiated by thelocally-irradiating means so as to cause the substrate and the mask toapproach each other locally; and a control means for controlling theslight-moving means based on a value measured by the gap-measuring meansand a preset value.
 5. The exposure apparatus as claim in claim 1,further comprising:a gap-adjusting means for adjusting the gap betweenthe substrate and the mask, a mask face-measuring means, positioned on amask side, for scanning the mask synchronously with a movement of thelocally-irradiating means so as to detect a height of a mask face of themask in a portion thereof irradiated by the locally-irradiating means;and a substrate face-measuring means, positioned on a substrate side,for scanning the substrate synchronously with a movement of thelocally-irradiating means so as to detect a height of a substrate faceof the substrate in a portion thereof irradiated by thelocally-irradiating means, and wherein the control means determines thegap between the substrate and the mask indirectly by calibrating adifference between the value measured by the mask face-measuring meansand the value measured by the substrate face-measuring means and basedon the value measured by the mask face-measuring means and the valuemeasured by the substrate face-measuring means, thus controlling thegap-adjusting means based on a value of the gap found determinedindirectly and the preset value.
 6. The exposure apparatus as claimed inclaim 5, wherein the mask face-measuring means and the substrateface-measuring means cooperate with each other so as to constitute thegap-adjusting means.
 7. The exposure apparatus as claimed in claim 6,wherein each of the mask face-measuring means and the substrateface-measuring means is composed of a laser reflection type measuringdevice.
 8. The exposure apparatus as claim in claim 4, furthercomprising:a gap-adjusting means for adjusting the gap between thesubstrate and the mask, a mask face-measuring means, positioned on amask side, for scanning the mask synchronously with a movement of thelocally-irradiating means so as to detect a height of a mask face of themask in a portion thereof irradiated by the locally-irradiating means;and a substrate face-measuring means, positioned on a substrate side,for scanning the substrate synchronously with a movement of thelocally-irradiating means so as to detect a height of a substrate faceof the substrate in a portion thereof irradiated by thelocally-irradiating means, and wherein the control means determines thegap between the substrate and the mask indirectly by calibrating adifference between the value measured by the mask face-measuring meansand the value measured by the substrate face-measuring means and basedon the value measured by the mask face-measuring means and the valuemeasured by the substrate face-measuring means, thus controlling thegap-adjusting means based on a value of the gap determined indirectlyand the preset value.
 9. The exposure apparatus as claimed in claim 8,wherein the mask face-measuring means and the substrate face-measuringmeans cooperate with each other so as to constitute the gap-adjustingmeans.
 10. The exposure apparatus as claimed in claim 9, wherein each ofthe mask face-measuring means and the substrate face-measuring means iscomposed of a laser reflection type measuring device.